The present invention relates to a protective filter for an extracorporeal circulation circuit pressure monitor. More specifically, the present invention relates to a protective filter for an extracorporeal circulation circuit pressure monitor which can reduce a load on a hydrophobic filter caused by pulsation of blood in a hemocatharsis therapy.
In an established hemocatharsis therapy such as hemodialysis, when blood is circulated to the extracorporeal circulation circuit by using a blood pump, the pressure of the blood in the extracorporeal circulation circuit is measured and a pressure fluctuation thereof is sensed. The pressure of blood in the extracorporeal circulation circuit is found by measuring a pressure transmitted to air contacting the blood in a drip chamber or the like with a pressure gage which is provided in the dialysis device through a pressure monitor line.
Usually, only air is filled in the pressure monitor line. However, in a case where an excessive pressure occurs in an inside of the extracorporeal circulation circuit by an increase in circulating blood flow rate, blood coagulation in the extracorporeal circulation circuit or an artificial kidney, or the like, blood enters into this pressure monitor line. If the blood reaches the pressure gage in the dialysis device, there is a problem that it becomes impossible to accurately measure the pressure in the extracorporeal circulation circuit. Further, if the blood or a blood-derived substance which has entered into an inside of the pressure gage reversibly flows to the extracorporeal circulation circuit, there is also a problem that it causes an infection.
Therefore, a conventional extracorporeal circulation circuit pressure monitor has a constitution in which there is provided a protective filter constituted by a dialysis device side housing, an extracorporeal circulation circuit side housing and a hydrophobic filter held between the housings (for example, Japanese Patent Laid-Open No. 2001-129079). The protective filter prevents blood or the like from entering into the inside of the pressure gage. In a conventional protective filter, a protective plate is vertically provided in a housing in order to support the hydrophobic filter in the housing. This protective plate is formed in order to suppress bulging of the hydrophobic filter and to prevent breaking of the filter. However, if the hydrophobic filter is caused to vibrate by pulsation of blood flowing in the extracorporeal circulation circuit, there is a problem that a portion of the filter which contacts the protective plate is broken by friction and that the blood leaks therefrom.
There is also developed a protective filter which is designed to prevent breakage of the filter (for example, Japanese Patent Laid-Open No. 2004-337287). The protective filter is comprised of an air pressure buffer member formed in the housing. The pressure on the filter is dispersed thereby and a load is prevented from being directly applied to the filter by the fluctuation of the pressure in the extracorporeal circulation circuit side. However, there is a problem also in this protective filter that the filter contacts the air pressure buffer member and is broken by the vibration of the filter due to the pulsation of the blood, so that an issue of blood leakage still exists.